Ag Foil Research Articles

Electrically motivated atomic migration and defect formation in Bi0.5Sb1.5Te3 compounds

Current-induced Ag migration behavior and defect formation mechanism in p-type Bi0.5Sb1.5Te3 (BST) compounds are investigated. By applying an electric current of 170 A/cm2 through a hot-pressed BST at 150 °C with one side attached to a thin Ag foil, Ag2Te secondary phases precipitate first in the BST and decompose subsequently after extended current stressing time. Ag elements migrate in BST toward the cathode side with a D⋅Z* product of 8 × 10−7 cm2/s, where D and Z* are diffusivity and electromigration effective charge number of Ag in BST, respectively. The van der Waals gap between two neighboring Te layers is identified to be the major path for Ag electromigration. Electrically motivated Ag atoms take Sb lattice sites eventually by forming AgSb acceptor defects in BST. The electrical resistivity of current-stressed BST was lowered by one order of magnitude as a result of greatly increased carrier concentration. The study demonstrates a route of adjusting electrical properties of BST compounds through the current-induced doping process.

Low-pressure solid-state bonding technology using fine-grained silver foils for high-temperature electronics

A solid-state bonding technique using fine-grained silver (Ag) foils is presented. The Ag foils are manufactured using many runs of cold rolling and subsequent annealing processes to achieve the favorable microstructure. X-ray diffraction and pole figure measurement are performed to examine the crystal structure and grain orientations. Si chips are bonded to bare Cu substrates using the Ag foil as the bonding medium at 300 °C in 0.1 torr vacuum assisted by 6.9 MPa static pressure, which is much lower than that used in conventional thermal compression bonding. Cross sections prepared by focus ion beam show clear bonding interfaces with only a few voids smaller than 100 nm. The bonded structures do not crack after cooling down to room temperature, indicating that the ductile Ag layer is able to manage the strain induced by the large coefficient of thermal expansion mismatch between Si and Cu. The average shear strength of as-bonded samples is 29 MPa. High-temperature storage tests are conducted, and slight increase in strength can be observed after 300 °C aging. Fracture analyses show that the breakage occurs within the Ag foil rather than on the bonding interface. Transmission electron microscopy and energy-dispersive spectroscopy (TEM/EDX) are conducted for Ag/Cu interface after 200-h aging, and the result shows that slight diffusion proceeds during the aging. Since Ag has the highest electrical and thermal conductivities among metals, therefore the bonded structures reported in this paper probably represent the best possible design for high-temperature and high-power electronic packaging applications.

Towards manufacturing technology: Balteus belt–fittings from the Wielbark culture cemetery in Linowo (Poland)

This study characterizes extraordinary Balteus belt–fittings recovered from the Wielbark culture cemetery in Linowo (Chełmno land, Poland). The belt–fittings were cast in Cu–alloys and decorated with embossed applications made of noble metals. Among the belt–fittings, some other grave inventory was also placed with the deceased.The metal inventory was described in terms of its composition and structure. The investigations were performed by means of the energy dispersive X–ray fluorescence spectroscopy (EDXRF). In order to fingerprint the Balteus belt–fittings manufacturing technology, the investigations involved the employment of the scanning electron microscopy (SEM) coupled with the energy dispersive X–ray analysis system (EDS) and optical microscopy (OM).The elemental composition indicates the application of two main types of Cu–alloys, i.e. scrap bronze (Cu–Sn, Cu–Sn–Pb, Cu–Pb–Sn) and scrap leaded gunmetal (Cu–Sn–Pb–Zn). It has been established that the Barbarian metalworkers were familiar with embossing the Au–Ag foils and made themselves capable of attaching them to a metal background with Sn–Pb solder. Based on the metallographic data, the reconstruction of the chaîne opératoire used for manufacturing the belt–fittings was implemented in this study as well.

Silver Nanowire/Carbon Sheet Composites for Electrochemical Syngas Generation with Tunable H2/CO Ratios.

Generating syngas (H2 and CO mixture) from electrochemically reduced CO2 in an aqueous solution is one of the sustainable strategies utilizing atmospheric CO2 in value-added products. However, a conventional single-component metal catalyst, such as Ag, Au, or Zn, exhibits potential-dependent CO2 reduction selectivity, which could result in temporal variation of syngas composition and limit its use in large-scale electrochemical syngas production. Herein, we demonstrate the use of Ag nanowire (NW)/porous carbon sheet composite catalysts in the generation of syngas with tunable H2/CO ratios having a large potential window to resist power fluctuation. These Ag NW/carbon sheet composite catalysts have a potential window increased by 10 times for generating syngas with the proper H2/CO ratio (1.7–2.15) for the Fischer–Tropsch process and an increased syngas production rate of about 19 times compared to that of a Ag foil. Additionally, we tuned the H2/CO ratio from ∼2 to ∼10 by adjusting only the quantity of the Ag NWs under the given electrode potential. We believe that our Ag NW/carbon sheet composite provides new possibilities for designing electrode structures with a large potential window and controlled CO2 reduction products in aqueous solutions.

SiC power devices packaging with a short-circuit failure mode capability

The failure mode of press-pack-type packages dedicated to SiC devices is experimentally analyzed in order to investigate their use for HVDC applications. Single SiC Schottky diode samples have been submitted to short-circuit conditions and continuous current flow test. The samples have been then characterized with optical and scanning electronic microscopy. Results from the experiments reveal that the press-pack structure offers a short-circuit failure mode with SiC devices, as it does for Si devices. The metallurgy involved is, however, quite different. Cu, Ni, Ag or Al foils are found to be suitable interface material between the package and the die to achieve a stable a short-circuit failure mode, providing the die is properly attached to a substrate.

Efficient photodegradation of dye pollutants using a novel plasmonic AgCl microrods array and photo-optimized surface-enhanced Raman scattering

A novel arrayed AgCl micro-rods have in situ grown on an Ag foil successfully for the first time. The preparation process is consisted of two facile steps: (1) immersed oxidation and (2) directional ions exchange. The structure of the as-synthesized arrayed substrate has been characterized comprehensively, and the relevant growth mechanism is proposed. This highly aligned AgCl arrays show a remarkable visible-light-driven photocatalytic activity towards degrading 10−5mol/L rhodamine 6G (R6G) aqueous solution. The ultra-stable catalytic performance of the plasmonic arrays was revealed by the recycled tests in the neutral and acidic conditions. Moreover, a facile SERS substrate based on the AgCl arrays was obtained with the optimal enhancement factor (EF) of ∼3.25×107, by directly putting the substrate under a Xe lamp in 7.5min. Amazingly, the photo-optimized surface-enhanced Raman scattering (SERS) substrate still shows a stable activity for photodegrading R6G. The photocatalytic and SERS mechanism are proposed in this study.

Interconnect Materials Enabling IGBT Modules to Achieve Stable Short-Circuit Failure Behavior

Insulated gate bipolar transistor (IGBT) modules, which can fail to stable short-circuit mode, have major applications in electricity network-related fields. Sn-3.5Ag solder joints and sintered Ag joints for the die attachment and Mo, Cu, Sn-3.5Ag, Al, and Ag foils for the top side insert (TSI) material in press pack like single IGBT samples have been investigated using overcurrent and current passage tests. The results reveal that Sn-3.5Ag solder joints in combination with Sn-3.5Ag, Al, or Ag foils can be employed to achieve stable short-circuit failure mode, where the best results are achieved with Ag foils. This can be attributed to the formation of conductive networks/channels through the failed IGBT and good alignment between the residual TSI material and the failed IGBT.

Anisotropic Mg Electrodeposition and Alloying with Ag-based Anodes from Non-Coordinating Mixed-Metal Borohydride Electrolytes for Mg Hybrid Batteries

A highly anisotropic electrodeposition was observed using the hybrid battery electrolyte Mg(BH4)2 with LiBH4 in diglyme. At low overpotentials high aspect ratio platelet morphologies are observed with a strong fiber texture composed of a {10-10} and a {11-20} component, the first evidence of behavior of this kind in magnesium battery electrolytes. At high overpotentials the deposit aspect ratio is indistinguishable but the texture is shown to be primarily composed of a {11-20} fiber texture. The kinetic parameters relative to the relevant crystallographic faces are extracted from electron microscopy images and compared with the observed bulk rate extracted from the electrochemical data. The use of polycrystalline Ag foil substrates with little preferred orientation at the surface allowed highly polycrystalline nucleation at lower overpotentials than that of platinum, likely due to Ag alloying with Mg. Characterization using focused ion beam (FIB) cross-sections with Auger Electron Spectroscopy (AES) elemental analysis confirm that the deposits are primarily Mg although Mg‐Ag alloys of various compositions were observed. It is proposed that the orientation at slow rates of growth is due to the underlying kinetics of adatom diffusion on Mg and that higher rates diminish the phenomenon due to decreased time for adatom diffusion and instead are governed by the rates of adatom formation or more specifically the adatom vacancy formation on the different low-index planes of Mg.

Identifying Key Factors towards Highly Reflective Silver Coatings

This paper attempts to identify key factor(s) for highly reflective silver (Ag) coatings. Investigation was made over the crystal orientation and surface roughness, using several types of surfaces, including electroplated Ag polycrystal films, physical vapour deposited polycrystal Ag films, and single crystal Ag foils with different crystal orientations. In each type of the surfaces, surface roughness was varied so that, for different combinations of crystal orientation, roughness would elucidate the key factors towards highly reflective Ag coatings. It is found that surface roughness plays a critical role in determining the reflectance, while the crystal orientation has negligible effect. The mean reflectance and one-way ANOVA analysis indicate that the single crystal Ag foils with three orientations performed statistically the same in the same roughness group at significance levelα= 0.05. Moreover, correlation between the surface reflectance and surface roughness has been proposed for the benefit of coating design. Refection data obtained from the polycrystalline silver samples are used to verify the accuracy of the proposed correlations. It was observed that the development surface area ratio,Sdr, is a better roughness indicator in predicting the reflectance of polycrystalline silver films than the arithmetic average roughness,Ra.

Influence of Alloying on CO2 Electroreduction on Ag-Zn System

Electrochemical reduction of CO2 is an attractive pathway for the sustainable production of fuels and chemicals, as it allows for the effective use of renewable energy sources while mitigating the effects of CO2 in the atmosphere. While significant decrease in overpotentials and increase in reaction rates have been reported for the two-electron reduction products, reports on improved activity and selectivity for the products that require more than two electrons (> 2 e- products) have been limited on monometallic transition metal catalysts. Recent theoretical work indicates that this difficulty of reducing CO2 to > 2 e- products is due to the linear scaling of the binding energies of CO2 reduction intermediates on transition metal catalysts, and the necessity of catalyst systems that can break such scaling has been emphasized.(1) Alloys, which can provide bifunctional sites that selectively stabilize intermediates, are a promising class of materials, and a large amount of effort has been focused on the investigation of their effectiveness as CO2 reduction catalysts. Recent works have reported on improved CO2 reduction activity and selectivity on alloy systems, which were attributed to the synergy between the two metal atoms at the surface. However, most improvements reported in these works are pertaining to two-electron products, and alloy systems that demonstrate improvements for > 2 e- products remain elusive. Here, we report on the investigation of polycrystalline AgZn foil, which resulted in the observation of enhanced activities and selectivities for methane and methanol productions compared to Ag and Zn foils. Although CO is the main CO2 reduction product as expected of an alloy between two metals active for CO production, the selective enhancement observed for the > 2 e- products is noteworthy, as it indicates that alloys are promising candidates in the development of effective CO2 electroreduction catalysts. The production of CO as major product is explained by the binding energies of intermediates, and the importance of optimal binding energies are discussed. Reference 1. A. A. Peterson and J. K. Nørskov, The Journal of Physical Chemistry Letters, 3, 251 (2012).

Enhanced CO selectivity and stability for electrocatalytic reduction of CO2 on electrodeposited nanostructured porous Ag electrode

Nanostructured electrocatalysts for CO2 reduction have attracted much attention due to their unique properties compared to their bulk counterparts. Here we report the synthesis of porous Ag foams on a polished Ag substrate via electrodeposition using the hydrogen bubble dynamic template. The as-prepared porous Ag foams has an average pore size of 10–25μm with the porous wall composed of 40–100nm Ag nanoparticles. CV tests indicate that the competing hydrogen evolution reaction remarkably slow down on porous Ag electrode and the onset potential of CO2 reduction occurs at 0.15V less than that on the Ag foil electrode. Moreover, the high current density and CO faradaic efficiency of over 90% were stable over the course of several hours, whereas Ag foil electrode exhibited the drop of CO faradaic efficiency from 74.4% to 58.6% under identical conditions. We found that the enhanced activity and stability are the result of a large electrochemical surface area (approximately 120 times larger) which can provide more active sites. The noteworthy difference between the two electrodes suggests that the nanostructured surface of porous Ag foams is likely to not only favor the formation of CO2− intermediate but also suppress the competitive reaction of hydrogen evolution.

Screen-printed BiFeO3 thick films on noble metal foils

ABSTRACTThis study presents microstructural and phase compositional characterization of 30-μm-thick bismuth ferrite (BiFeO3) films screen-printed on Ag, Au and Pt metal foils. Ag is shown to be chemically incompatible with BiFeO3 at temperatures higher than 750°C. X-ray diffraction and scanning electron microscopy analysis reveal that an almost single phase BiFeO3 thick film can be obtained on Au and Pt substrates after sintering at 750°C, while sintering at 820°C results in increased densification of BiFeO3. This work represents another step further towards the integration of BiFeO3 into thick film structures.

Highly improved voltage efficiency of seawater battery by use of chloride ion capturing electrode

Cost-effective and eco-friendly battery system with high energy density is highly desirable. Herein, we report a seawater battery with a high voltage efficiency, in which a chloride ion-capturing electrode (CICE) consisting of Ag foil is utilized as the cathode. The use of Ag as the cathode leads to a sharp decrease in the voltage gaps between charge and discharge curves, based on reversible redox reaction of Ag/AgCl (at ∼2.9 V vs. Na+/Na) in a seawater catholyte during cycling. The Ag/AgCl reaction proves to be highly reversible during battery cycling. The battery employing the Ag electrode shows excellent cycling performance with a high Coulombic efficiency (98.6–98.7%) and a highly improved voltage efficiency (90.3% compared to 73% for carbonaceous cathode) during 20 cycles (total 500 h). These findings demonstrate that seawater batteries using a CICE could be used as next-generation batteries for large-scale stationary energy storage plants.

Fabrication of activation foil arrays using printing techniques for evaluation of spatial distribution of neutron flux and energy

Since the activation foil and threshold detector arrays for evaluating the spatial distributions of neutron flux and energy, respectively, have traditionally been manufactured by hand, it was difficult to achieve the precise array density. In this study, a dense foil array with a precision of ≤6 µm was successfully fabricated by using a jet dispenser and printing device to arrange 100 Ag foils in an area of 16 cm2, and a complex array of Ag and Ti foils was engineered with the same precision. As the result, high-resolution spatial distributions of the flux can be measured by more dense activation foil arrays.

The detection of reverse accumulation effect in the positron annihilation profile of stack of aluminum and silver foils

Abstract The implantation profile of positrons emitted from 22Na into a stack of aluminum and silver foils is the subject of the presented report. The characteristic dimple in the profile behind the Ag foil was detected. This effect arises from the differences in the linear absorption coefficient of aluminum and silver. The good agreement between the theoretical profile obtained within the multiscattering model and experimental one was achieved. The observed phenomenon can affect the positron annihilation characteristics measured for the inhomogeneous samples.

Achieving Selective and Efficient Electrocatalytic Activity for CO2 Reduction Using Immobilized Silver Nanoparticles.

Selective electrochemical reduction of CO2 is one of the most sought-after processes because of the potential to convert a harmful greenhouse gas to a useful chemical. We have discovered that immobilized Ag nanoparticles supported on carbon exhibit enhanced Faradaic efficiency and a lower overpotential for selective reduction of CO2 to CO. These electrocatalysts were synthesized directly on the carbon support by a facile one-pot method using a cysteamine anchoring agent resulting in controlled monodispersed particle sizes. These synthesized Ag/C electrodes showed improved activities, specifically decrease of the overpotential by 300 mV at 1 mA/cm(2), and 4-fold enhanced CO Faradaic efficiency at -0.75 V vs RHE with the optimal particle size of 5 nm compared to polycrystalline Ag foil. DFT calculations enlightened that the specific interaction between Ag nanoparticle and the anchoring agents modified the catalyst surface to have a selectively higher affinity to the intermediate COOH over CO, which effectively lowers the overpotential.

Effect of Chloride Anions on the Synthesis and Enhanced Catalytic Activity of Silver Nanocoral Electrodes for CO2 Electroreduction

Metallic silver (Ag) is known as an efficient electrocatalyst for the conversion of carbon dioxide (CO2) to carbon monoxide (CO) in aqueous or nonaqueous electrolytes. However, polycrystalline silver electrocatalysts require significant overpotentials in order to achieve high selectivity toward CO2 reduction, as compared to the side reaction of hydrogen evolution. Here we report a high-surface-area Ag nanocoral catalyst, fabricated by an oxidation–reduction method in the presence of chloride anions in an aqueous medium, for the electro-reduction of CO2 to CO with a current efficiency of 95% at the low overpotential of 0.37 V and the current density of 2 mA cm–2. A lower limit of TOF of 0.4 s–1 and TON > 8.8 × 104 (over 72 h) was estimated for the Ag nanocoral catalyst at an overpotential of 0.49 V. The Ag nanocoral catalyst demonstrated a 32-fold enhancement in surface-area-normalized activity, at an overpotential of 0.49 V, as compared to Ag foil. We found that, in addition to the effect on nanomorpholog...

Enhancement in carbon dioxide activity and stability on nanostructured silver electrode and the role of oxygen

Current energy production habits deplete fossil fuels and accumulate atmospheric CO2, which contribute to the global climate change. Electrochemical fuel production via CO2 reduction reaction is an idealistic yet an achievable process that mitigates CO2 emissions and simultaneously satisfies energy demands. Here, the enhancement of CO2 reduction activity and stability on size-controlled particulate Ag electrocatalysts derived from a simple, one-step cyclic voltammetry (CV) process by changing scan rates (1–200mV/s) was demonstrated. Interestingly, larger nanoparticles prepared by slower scan rates (1–5mV/s) have exhibited the most degree of enhancement for CO2 reduction to CO product. Compared to untreated Ag foil, nanostructured Ag electrode has shown an anodic shift of approximately 200mV in the onset potential of CO partial current density (jCO), 160mV reduction of overpotential at jCO=10mA/cm2, and increased Faradaic efficiency (F.E.) for CO production especially at lower biased potentials (−0.89 to −1.19V vs. RHE). Stability tests have demonstrated a drastic improvement in maintaining CO F.E. X-ray photoelectron spectroscopy suggests that the enhancement is associated with stable oxygen species incorporated on the nanoparticle Ag surfaces during the CV fabrication process.

Energy loss and straggling of α-particles in Ag and Sn metallic foils

Energy loss and straggling in Ag and Sn metallic foils for α-particles, using 241Am source, are measured. The measured energy loss values are compared with the predicted values based on Benton and Henke, Grande and Schiwietz (CasP), Ziegler et al. (SRIM) formulations and ICRU-49 report (ASTAR). Also, measured straggling values of α-particles are compared with the computed values adopting practically used four collisional (Bohr, Lindhard and Scharff, Bethe–Livingston, Titeica) formulations and one collisional plus charge exchange (Yang et al.) straggling formulation. The aim of the comparison is to identify the best energy loss and straggling formulation.

Study of metal specific interaction, F-LUMO and VL shift to understand interface of CuPc thin films and noble metal surfaces

The performances of organic electronic devices are significantly associated with their energy level alignment at organic semiconductor/metal–electrode interfaces. The electronic character of an organic semiconducting molecular over-layer on a metal surface can vary from semiconducting to metallic, depending on the nature of the molecular orbitals with respect to the Fermi level of the electrode. The general tendency of extrapolating established models for single crystal substrates to ‘real’ device substrates is highly misleading. Hence, the importance of metal specific interaction, former lowest unoccupied molecular orbital (F-LUMO) and vacuum level (VL) shift have been investigated as a function of thickness of the deposited films by means of photoelectron spectroscopy (XPS and UPS) to understand the interface between CuPc and Cu, Ag, Pt and Au foils sequentially. The XPS data provides the signature of affectability of pyrrole sites of CuPc molecules for partial charge transfer from Cu and Ag substrates while a negligible effect on pyrrole cites resulted for Pt and Au substrates. Furthermore, the appearance of F-LUMO, a hybridized state close to the Fermi level gives confirmatory information about partial charge transfer. Contrary to the general belief that vacuum level shift caused by charge transfer can partially or totally cancel that for push back effect, our observation indicates that the partial charge transfer does not play significant role in the shift of vacuum level. The entire thickness dependent electronic energy level alignment of CuPc films on all noble metal substrates is explained in terms of a combined effect of partial charge transfer and photoemission final state relaxation energy. A systematic variation of HOMO-FWHM was observed with CuPc thickness due to continuous change in molecular orientation.